DBI connect problem

Marcello has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I use the following routine in a package to connect to a MySQL database on a Linux system (with a lot of debugging stuff to solve my problem):

sub db_connect {
    my $self = shift;

    my $errStr;
    my $testStr;
    my $dbh;
    eval {
        local $SIG{ALRM} = sub { die "timeout\n" }; # NB: \n required
        alarm 10;
        $dbh = DBI->connect("DBI:mysql:".$self->{DB_NAME}.":".$self->{
+DB_HOSTNAME}.":".$self->{DB_PORT}, $self->{DB_USERNAME}, $self->{DB_P
+ASSWORD}, { PrintError => 0 });
        if (defined($dbh)) {
            $testStr = "[Database handle SET]";
        }
        else {
            $errStr = "Unable to connect to database: ".$DBI::errstr;
            $testStr = "[Database handle NOT SET]";
        }
        alarm 0;
    };
    if ($@ eq "timeout\n") {
        # Timeout
        $errStr = "Connection to database timed out";
    }
    elsif ($@) {
        # Unknown error
        $errStr = "Unknown error: ".$@;
    }

    my $result = defined($dbh);
    if (!$result) {
        $errStr .= " [dbh DEFINED]".$testStr;
    }
    else {
        $errStr .= " [dbh UNDEFINED]".$testStr;
        $self->log_comment("ERROR: db_connect => ".$errStr);
    }
    return $result;
}
[download]

I use a timeout on the database connect, the parameters to the DBI->connect routine are OK. Almost always the connection is succesful, but sometimes this line shows up in the logfile:

2002-07-30 21:48:31: ERROR: db_connect => dbh UNDEFINED

So the DBI->connect failed, but I don't know why. It seems to me that $errStr should always have a value and when the connect does NOT timeout, $testStr also. But the logfile shows otherwise!

I am missing something... but what and where?

TIA, Marcel

Comment on DBI connect problem Download Code

Replies are listed 'Best First'.
Re: DBI connect problem by Ovid (Cardinal) on Jul 30, 2002 at 20:27 UTC
Try using `RaiseError` and an "or die" statement: `my $dbh = DBI->connect( "DBI:mysql:$self->{DB_NAME}:$self->{DB_HOSTNAME}:$self->{DB_PORT}" +, $self->{DB_USERNAME}, $self->{DB_PASSWORD}, { PrintError => 0, RaiseError => 1, } ) or croak DBI->errstr;` [download] Cheers, Ovid Join the Perlmonks Setiathome Group or just click on the the link and check out our stats.	[reply] [d/l]
Re: DBI connect problem by hiseldl (Priest) on Jul 30, 2002 at 20:33 UTC
It seems as though your logic is backwards... `my $result = defined($dbh);` ...so far so good... `if (!$result) {` ...this is saying if `$result` is not defined, and this does not correlate with your statements... you should change `if (!$result) {` to `if (!defined($dbh) ) {` giving the following code, which should make more sense `if (!defined($dbh) ) { $errStr .= " [dbh UNDEFINED]".$testStr; $self->log_comment("ERROR: db_connect => ".$errStr); } else { $errStr .= " [dbh DEFINED]".$testStr; }` [download] -- hiseldl	[reply] [d/l] [select]
Swap branches refactoring by IlyaM (Parson) on Jul 31, 2002 at 08:02 UTC
I would refactor code like `if (!defined($dbh) ) { $errStr .= " [dbh UNDEFINED]".$testStr; $self->log_comment("ERROR: db_connect => ".$errStr); } else { $errStr .= " [dbh DEFINED]".$testStr; }` [download] into `if (defined $dbh) { $errStr .= " [dbh DEFINED]".$testStr; } else { $errStr .= " [dbh UNDEFINED]".$testStr; $self->log_comment("ERROR: db_connect => ".$errStr); }` [download] Idea of this refactoring is that if you have an if/else construct it makes sense to swap branches if it simplifies the condition. -- Ilya Martynov (http://martynov.org/)	[reply] [d/l] [select]
Re: DBI connect problem by Cine (Friar) on Jul 30, 2002 at 20:25 UTC
I can only see one way: DBI dies, but does not set $@. Try setting RaiseError => 0 T I M T O W T D I	[reply]